linux-kernel - Re: [PATCH] ext4: fix possible memory leak when enable bigalloc feature

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Date:   Mon, 7 Nov 2022 14:46:38 +0100
From:   Jan Kara <jack@...e.cz>
To:     Ye Bin <yebin@...weicloud.com>
Cc:     tytso@....edu, adilger.kernel@...ger.ca,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        jack@...e.cz, Ye Bin <yebin10@...wei.com>,
        syzbot+05a0f0ccab4a25626e38@...kaller.appspotmail.com,
        Eric Whitney <enwlinux@...il.com>
Subject: Re: [PATCH] ext4: fix possible memory leak when enable bigalloc
 feature

Let me CC Eric who wrote this code...

On Mon 07-11-22 09:54:15, Ye Bin wrote:
> From: Ye Bin <yebin10@...wei.com>
> 
> Syzbot found the following issue:
> BUG: memory leak
> unreferenced object 0xffff8881bde17420 (size 32):
>   comm "rep", pid 2327, jiffies 4295381963 (age 32.265s)
>   hex dump (first 32 bytes):
>     01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<00000000ac6d38f8>] __insert_pending+0x13c/0x2d0
>     [<00000000d717de3b>] ext4_es_insert_delayed_block+0x399/0x4e0
>     [<000000004be03913>] ext4_da_map_blocks.constprop.0+0x739/0xfa0
>     [<00000000885a832a>] ext4_da_get_block_prep+0x10c/0x440
>     [<0000000029b7f8ef>] __block_write_begin_int+0x28d/0x860
>     [<00000000e182ebc3>] ext4_da_write_inline_data_begin+0x2d1/0xf30
>     [<00000000ced0c8a2>] ext4_da_write_begin+0x612/0x860
>     [<000000008d5f27fa>] generic_perform_write+0x215/0x4d0
>     [<00000000552c1cde>] ext4_buffered_write_iter+0x101/0x3b0
>     [<0000000052177ae8>] do_iter_readv_writev+0x19f/0x340
>     [<000000004b9de834>] do_iter_write+0x13b/0x650
>     [<00000000e2401b9b>] iter_file_splice_write+0x5a5/0xab0
>     [<0000000023aa5d90>] direct_splice_actor+0x103/0x1e0
>     [<0000000089e00fc1>] splice_direct_to_actor+0x2c9/0x7b0
>     [<000000004386851e>] do_splice_direct+0x159/0x280
>     [<00000000b567e609>] do_sendfile+0x932/0x1200
> 
> Now, 'ext4_clear_inode' don't cleanup pending tree which will lead to memory
> leak.
> To solve above issue, cleanup pending tree when clear inode.
> 
> Reported-by: syzbot+05a0f0ccab4a25626e38@...kaller.appspotmail.com
> Signed-off-by: Ye Bin <yebin10@...wei.com>

So I'd think that by the time we are freeing inode all pending reservations
should be resolved and thus the tree should be empty. In that case you'd be
just masking some other bug where we failed to cleanup pending information
at the right moment. But maybe I'm missing something - that's why I've
added Eric to have a look ;)

								Honza

> ---
>  fs/ext4/extents_status.c | 22 ++++++++++++++++++++++
>  fs/ext4/extents_status.h |  1 +
>  fs/ext4/super.c          |  1 +
>  3 files changed, 24 insertions(+)
> 
> diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
> index cd0a861853e3..5f6b218464de 100644
> --- a/fs/ext4/extents_status.c
> +++ b/fs/ext4/extents_status.c
> @@ -1947,6 +1947,28 @@ void ext4_remove_pending(struct inode *inode, ext4_lblk_t lblk)
>  	write_unlock(&ei->i_es_lock);
>  }
>  
> +void ext4_clear_inode_pending(struct inode *inode)
> +{
> +	struct ext4_inode_info *ei = EXT4_I(inode);
> +	struct pending_reservation *pr;
> +	struct ext4_pending_tree *tree;
> +	struct rb_node *node;
> +
> +	if (EXT4_SB(inode->i_sb)->s_cluster_ratio == 1)
> +		return;
> +
> +	write_lock(&ei->i_es_lock);
> +	tree = &EXT4_I(inode)->i_pending_tree;
> +	node = rb_first(&tree->root);
> +	while (node) {
> +		pr = rb_entry(node, struct pending_reservation, rb_node);
> +		node = rb_next(node);
> +		rb_erase(&pr->rb_node, &tree->root);
> +		kmem_cache_free(ext4_pending_cachep, pr);
> +	}
> +	write_unlock(&ei->i_es_lock);
> +}
> +
>  /*
>   * ext4_is_pending - determine whether a cluster has a pending reservation
>   *                   on it
> diff --git a/fs/ext4/extents_status.h b/fs/ext4/extents_status.h
> index 4ec30a798260..25b605309c06 100644
> --- a/fs/ext4/extents_status.h
> +++ b/fs/ext4/extents_status.h
> @@ -248,6 +248,7 @@ extern int __init ext4_init_pending(void);
>  extern void ext4_exit_pending(void);
>  extern void ext4_init_pending_tree(struct ext4_pending_tree *tree);
>  extern void ext4_remove_pending(struct inode *inode, ext4_lblk_t lblk);
> +extern void ext4_clear_inode_pending(struct inode *inode);
>  extern bool ext4_is_pending(struct inode *inode, ext4_lblk_t lblk);
>  extern int ext4_es_insert_delayed_block(struct inode *inode, ext4_lblk_t lblk,
>  					bool allocated);
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 106fb06e24e8..160667dcf09a 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1434,6 +1434,7 @@ void ext4_clear_inode(struct inode *inode)
>  	clear_inode(inode);
>  	ext4_discard_preallocations(inode, 0);
>  	ext4_es_remove_extent(inode, 0, EXT_MAX_BLOCKS);
> +	ext4_clear_inode_pending(inode);
>  	dquot_drop(inode);
>  	if (EXT4_I(inode)->jinode) {
>  		jbd2_journal_release_jbd_inode(EXT4_JOURNAL(inode),
> -- 
> 2.31.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR